388 Background: To investigate acquired resistance of clear cell renal cell cancer (ccRCC) patients to sunitinib and develop personalised treatment strategies, sequential tissue after a specific period of targeted therapy is required. This approach has proven successful with targeted therapy in chronic myeloid leukaemia; however, we are concerned that extensive tumour heterogeneity occurs in ccRCC. In this study we evaluated heterogeneity and differential protein expression in sunitinib treated and untreated ccRCC samples using high-throughput proteomics.
METHODS
Fresh frozen tissue was obtained from 27 sunitinib naïve ccRCC specimens and 27 nephrectomy samples from patients treated with neoadjuvant sunitinib (18 weeks) as part of the SuMR trial. From each tumour frozen sections were performed and up to 5 protein lysates obtained from each morphologically differing region of each tumour as well as matched normal kidney. Reverse phase protein arrays (RPPA) were performed to assess the levels of multiple proteins relevant to ccRCC pathogenesis and sunitinib activity. Appropriate statistical tests were used to examine protein heterogeneity and differential expression, including false discovery rate (FDR) correction. Kaplan-Meier method was used to correlate changes in protein expression with outcome.
RESULTS
Expression of 20 proteins has been examined to date. The range of expression in tumours normalised by matched normal renal tissue had >2-fold differences in untreated (n=8 proteins) and treated samples (n=4 proteins). Four markers displayed significantly increased inter-tumoural variance in sunitinib treated tumours compared with untreated tissue (e.g. VEGFR1, FDR P<0.05). Despite this heterogeneity, sunitinib was associated with significant expression changes for several key proteins (e.g. VEGFR2, CyclinD2; FDR P<0.05).
CONCLUSIONS
Protein expression in ccRCC is heterogenous and key proteins showed significantly increased variance of expression with sunitinib therapy. Despite heterogeneity, significant changes in protein expression can be identified with sunitinib treatment and have been correlated with outcome.